Japanese Unexamined Patent Publication (Kokai) No. 2003-035959 discloses a method for treatment of a developing waste liquid of a negative photosensitive lithographic printing plate. This publication proposes that an inorganic flocculant and an organic polymer compound-based flocculant are used alone or in combination so as to treat a washing waste liquid.
Japanese Unexamined Patent Publication (Kokai) No. 06-27683 discloses a method for processing a non-silver salt photosensitive material using an automatic processor. This publication proposes a combination of flocculation treatment and filtration as one means for separating a washing waste water into a solute and water. The flocculation treatment is conducted by adding a neutralizing agent and/or a flocculant to the washing waste water. As the flocculent, an inorganic flocculant or an organic flocculant has been proposed.
Japanese Unexamined Patent Publication (Kokai) No. 04-334589 discloses a method for treatment of an exhausted washing liquid of a non-silver salt photosensitive material. This publication proposes that a filter aid and a neutralizing agent are used as flocculation means so as to treat the exhausted washing liquid.
Japanese Unexamined Patent Publication (Kokai) No. 04-353847 discloses a method for treatment of an exhausted washing liquid of a non-silver salt photosensitive material. This publication proposes that a two-stage filtration method is used after using a filter aid and a neutralizing agent as flocculation means.
Japanese Unexamined Patent Publication (Kokai) No. 07-020636 discloses a method for treatment of an exhausted washing liquid of a non-silver salt photosensitive material. This publication proposes that a two-stage filtration method is used after using a filter aid and a neutralizing agent as flocculation means, and that the filtrate is transferred to a second flocculation step or a third filtration step.
Japanese Unexamined Patent Publication (Kokai) No. 04-322784 discloses a method for treatment of a washing waste liquid of a photosensitive material. This publication proposes that the washing waste liquid is treated by a first flocculation step, a neutralization step and a second flocculation step. An inorganic flocculant is used in the first flocculation step, while a cationic polymer flocculant is used in the second flocculation step.
Japanese Unexamined Patent Publication (Kokai) No. 05-005998 discloses a method for treatment of a circulating washing liquid of a photosensitive lithographic printing plate. This publication proposes that the circulating washing liquid is subjected to a neutralization flocculation treatment. In the neutralization flocculation treatment, at least one treatment of addition of a neutralizing agent, addition of a filter aid and addition of a flocculant is used. In this publication, the flocculant is not specifically described.
These conventional flocculation methods are not suited for practical use since it is difficult to remove the precipitate produced after adding the flocculant through filtration because of tackiness and adhesion of the precipitate, and a long period of time is required in the case of gravity-flow filtration and also a high-degree separation apparatus, such as treatment by centrifugal filtration, press filtration or ultra filtration is required.